"The Russian side expressed its serious concern over the numerous victims among the civilian population and the grave humanitarian situation," the Kremlin said in a statement describing a telephone coversation between the two men.

"The Russian president also stressed the importance of a ceasefire as soon as possible."

Russia is a permanent member of the United Nations Security Council and one of the Quartet of Middle East mediators.

Alexander Saltanov, a deputy foreign minister and Medvedev's special envoy for the Middle East, flew to the region on Sunday to press for a ceasefire, the foreign ministry said.

Israeli troops and tanks invaded in the Gaza strip in an offensive against Gaza that has killed more than 500 Palestinians.